Results of physiological and psychological studies related to night and shift work are reviewed from the standpoint of their possible use by industry in understanding the problems of shift work and finding solutions. (New research data that has appeared since original preparation of the manuscript is presented in a three-part addendum with references to it incorporated into the main body of the text.) In Chapter I and Addenda VII and VIII circadian rhythms in biological functions are reviewed with emphasis on man's functional capacities during the day and night and the resulting variations in response to environmental factors as well as to work. Physical exertion in work is studied in Chapter II and Addendum IX, mental and sensory performance in Chapter III, and the effect of heat stress in Chapter IV. All of these chapters consider the question: should the same level of performance be expected from a night shift worker as from a daytime employee, and if not, how and to what extent would the requirements be modified? Chapter V stresses the importance of sleep after night work, and Chapter VI describes various shift systems as well as the scheduling of work times and breaks during the night shift. It is noted that since the results are discussed here in a descriptive manner, the causes of the observed variations are not always given. (ELG)